Bartolo bladder clover was collected from Cyprus (near the town of Melini) in 1987 by C. Francis, D. Drousiotis and A. Della. It has been developed by the Department of Primary Industries and Regional Development with the involvement of research officers Angelo Loi and Bradley Nutt, as part of the National Annual Pasture Legume Improvement Program.
Description and area of use
Bladder clover is a self-pollinating species and produces small pink flowers. Seeds are contained in a papery pod which is surrounded by a bladder-like, papery calyx; the basis for the common name of bladder clover. One inflorescence may produce up to 150 seeds. Individual seeds are round in shape, approximately 2mg in weight, and range in colour from yellow to orange brown.
Bartolo is a semi-erect cultivar, flowering approximately 105 days after emergence in Perth. It is adapted to sandy-loam and clay-loams soils of mildly acid to alkaline reaction (pH 5-8 CaCl2), provided it is reasonably fertile. It is not adapted to saline soils or to long periods of waterlogging.
Bladder clover has an advantage for seed-setting over subterranean clover on hard setting soils, where subterranean clover is unable to bury its burrs. Bartolo can be sown alone or is an ideal companion plant in mixtures with other legumes such as subterranean clover or yellow and French serradellas.
The quantity of forage produced by Bartolo is at least equivalent to current pasture such as subterranean clover or annual medics. Peak dry matter yields in ungrazed experimental swards have ranged between 4-7t/ha, depending on season and location. Seed yields are normally high ranging from 0.5-1t/ha. Seed is easily harvested using conventional grain harvesting machinery.
Severe frost at flowering can reduce seed production. Bartolo regenerates well in both continuous pasture and after rotational cropping. It has a hard seed level in the autumn following seed set of about 55%. This suggests that Bartolo has adequate hard seed levels for persistence in crop rotations but also makes it suitable for use in a phase farming system (short pasture phases of 1-3 years). The pattern of seedling emergence of Bartolo indicates it suffers less seedling loss from false breaks following un-seasonal rainfall.
The feeding value of Bartolo is similar to subterranean clover. Digestibility of Bartolo in spring can be as high as 82%, with 22% crude protein; these values decrease from late flowering to senescence. Grazing trials have shown no differences in liveweight change or wool growth between sheep grazing Bartolo and Dalkeith subterranean clover.
No livestock disorders have been reported with Bartolo but, as with most legumes, very pure bladder clover swards could cause bloat in cattle. Levels of the phyto-oestrogens formononetin (0.015%) and genistein (0.002%) in Bartolo are lower than in Dalkeith subterranean clover and are unlikely to cause infertility problems and difficult births in grazing animals.
Bladder clover should be treated as a seed crop in the year of establishment to ensure maximum seed set. Spray-top the paddock in the previous spring or select a paddock coming out of a cereal crop where broad-leaf weeds have been successfully controlled. Delay sowing in high rainfall regions to achieve good weed control with a knockdown herbicide.
In low rainfall regions sow bladder clover as close to the break of season as possible. Inoculation with Group C (strain WSM 1325) rhizobium is highly recommended. Sow from 5-10kg/ha if sown alone. Use lower rates if sown in mixtures with other pasture legumes. For optimal establishment sow bladder clover less than 2cm deep.
If machinery with precise seeding depth is not available this can be accomplished by dropping seed on the surface and covering with trailing harrows. Fertilise at sowing with at least 150kg/ha superphosphate or super-potash, if on sandy soils. Control redlegged earth mite until plants have three true leaves.